Apparatuses of this kind, which are referred to as water cooling sections, serve the purpose of cooling wire, which issues from the last rolling frame of a wire rolling mill prior to entry into a coiler, to lower the temperature as quickly as possible to the temperature required for the heat treatment of the wire. However, this cooling should not take place too abruptly, as otherwise the temperature difference between the wire core and the surface of the wire will become too great. The altered transformation conditions may then cause inhomogeneities in structure over the wire cross-section. Finally, the temperature should not fall below a safety temperature of about 500.degree. C., as otherwise there would be a risk of martensite formation.
A drawback of guide tubes, through which water flows, which has already been recognised is that the tip of the wire, on being introduced, is braked by pressure build-up of the water present in the guide tube. Because the wire tip bends (which is not possible to avoid) an additional component of movement is directed towards the tube wall, and this results in a high degree of friction. In this way the wire frequently breaks out of conventional water cooling sections. To avoid this disadvantage, it is known to release the inflow of water into the guide tubes only after the wire tips have been introduced. At the high wire speeds usual at the present time this procedure means that the first 50 to 100 meters of each coil are cooled in an uncontrolled manner and have to be rejected due to their non-uniform structure and their thick scale layer.
It is further known, for reducing the build-up of pressure when the wire is introduced, to produce a water/air mixture in the water filled guide tubes by blowing air into the latter. However, a uniform cooling effect is not ensured by this method owing to the inadequate mixing of the air and water in the guide tubes.